Marantz CD-73 - Strange noise while playing

[Marantzien]

Hello people,

I've just created an account on your forum, so nice to meet you.
I need your help guys about an old Marantz CD-73 CD player. In fact, when it reads a CD, you can ear a strange noise. It seems it comes from the motor or the lens but I'm not sure.

Click here to ear the noise

Have you ever had that kind of problem ?

Thanks

 

[Netlist]

Pitch and frequency goes along with the rotational speed of the CD. I think the CD clamp is dragging.
I also see that you turn a screw(?) which lifts the clamping mechanism. Why?

 

[Marantzien]

The screw is used to set the height (and weight I guess) of the clamp above the CD. I had to turn it because it wasn't properly set and so the motor had dificulties to work (you can ear it on the video when you start watching it).

 

[Marantzien]

I've just tried something while the deck was playing and making the noise.
I tried to make the speed of the motor lower to ear if there was any difference. And the result is : no difference, the sound is the same. Moreovoer, the sound goes away when I go to the next track. So I guess the problem comes from the lens. But the question is : why and how fix it ?

 

[Mooly]

It sounds like the radial drive motor (the swing arm) that you can hear. Its hard to judge just how loud it is in reality but the Philips RAFOC does make those kind of noises and particularly when jumping tracks such as going to the last track on a disc. In normal play mode it should not be obvious though.

This is what you are are hearing (this is your player) and the noise is centred around 1300Hz

Are there any adjustments on these for the radial drive? (I've not got a manual in front of me)

 

[Netlist]

If possible, remove the clamp mechanism and use an old cd and temporarily tape it to the spindle.

 

[Mooly]

This is what you are are hearing (this is your player) and the noise is centred around 1300Hz

I'll be quiet after this Its a long time since I worked on these... you start remembering things.

1300Hz, that's twice 650Hz and isn't 650Hz the frequency deliberately injected into the radial servo, with the tracking error waveform also at 650 Hz. I think that is what you are hearing

 

[Netlist]

Its a long time since I worked on these

Me too and I never heard that noise. We'll see..

 

[Mooly]

A very very long time actually

 

[Marantzien]

Hello Mooly,
Thanks for the information, the Marantz CD-73 manual is not complete and doesn't talk about lens adjustements (but it is in English at least). I can also use the Philips CD300/303 manual which is more complete but it's in German or Dutch only (I'm not lucky...). I'll have to translate it when I've got some time to kill.
Hugo, I tried what you propose but without any changes. I still can ear the noise. That let me think the noise comes from the lens.

 

[Netlist]

https://www.diyaudio.com/community/...ms-fine-voltages-differ-oddly-from-sm.363304/

I found this thread and I only read very quickly, but something similar here, with a solution in post #11 & #12. Perhaps there is some useful info for you.

 

[soulmerchant]

I restored two of these marantz 73's to like-new or better-than-new condition. But I never heard this sound before.

First step with all of these '80's philips machines is to replace all the electrolytic caps...

 

[Mooly]

First step with all of these '80's philips machines is to replace all the electrolytic caps...

Yes, I'm afraid it is really

 

[Marantzien]

Thanks Hugo, I'll look at it

First step with all of these '80's philips machines is to replace all the electrolytic caps...

Yes, all the caps are new and all the solders have been redone

 

[Netlist]

I'll look at it

I looked a bit more in dept and it not really the same problem but there's a lot of technical info.

 

[bram jacobse]

Hi, i had the same problem with a CD204 , fix it by tighten up bolts on the CDM-1

https://forum-mfbfreaks.nl/viewtopic.php?p=203013&hilit=1300#p203013

 

[profiguy]

Its a mechanical resonance from the swing arm pivoted coil. There is a cap parallel to the output for demodulating the servo output which gets weak. The cap has been changed in value of the production run. You need to increase the value slightly as well as the filtering choke in series. Some players didn't have the coil, only the cap. Its a bipolar electrolytic. Don't remember the size.